The goal of this clinical study is to evaluate the effectiveness, safety and patient experience of an integrated care pathway combining rapid antiretroviral (ART) initiation with BIC/FTC/TAF and peer navigation for treatment naïve newly-diagnosed or relinking HIV-infected PWIDs, in terms of viral suppression rates, adverse events and patient-reported health outcomes (PROs).

The main objectives of the study are the assessment of:

• The viral suppression rates at 24 weeks after the rapid initiation of ART with BIC/FTC/TAF coupled with secured peer-navigation in adult HIV-positive PWID who are treatment-naïve or re-linking to care
• The safety and tolerability of BIC/FTC/TAF in the specific context of rapid ART initiation in adult PWID who are treatment-naïve or re-linking to care from baseline until Week 24. Patients will receive their medication according to the standard of care and will visit the clinic as usual. No extra visits or extra lab tests will be performed.

Taking into account the increased rates of new cases of HIV infection among people who inject drugs (PWID) in Greece, it is proposed the conduct of the observational study with the aim to assess whether clinical outcomes can be improved by the implementation of rapid ART initiation in newly diagnosed HIV-positive PWIDs and re-linking to care previously diagnosed HIV-positive PWIDs with a suitable medication, such as BIC/FTC/TAF, combined with peer-navigation support that can help the afflicted patients overcome social barriers and challenges. Therefore, this pilot study aims to evaluate the effectiveness, safety and patient experience of an integrated care pathway combining rapid ART initiation with BIC/FTC/TAF and peer navigation for treatment naïve newly-diagnosed or relinking HIV-infected PWIDs, in terms of viral suppression rates, adverse events and patient-reported health outcomes (PROs). Given the armamentarium of potent ART regimens, HIV infection has been transformed from a terminal illness into a chronic condition, thus, evaluating the impact of ARTs from patients' perspective is increasingly used [17]. The results of this study are expected to contribute towards informed health policy practices, accelerating and ameliorating care and providing the basis to curb the HIV epidemic and bringing us closer to its end.

Inclusion Criteria:

1. Male or female PWID subjects ≥18 years old
2. Documented and confirmed diagnosis of HIV infection
3. Naïve to ART or having discontinued ART for more than 3 months and relinking to care without documented resistance to any of the components of BIC/FTC/TAF or having missed more than once during the last 12 months, their monthly appointment for ART prescription renewal.
4. Willingness of patients to start OST or already being in OST.
5. Subjects willing and able to understand and provide written informed consent prior to participation in the study.
6. Females may be eligible for enrolment if they are i) of non-child-bearing potential or ii) if they are of child-bearing potential must have a negative pregnancy test at initial screening and agree to use throughout the study a medically acceptable method of contraception (barrier and/or hormonal method) or iii) are sterilized.

Exclusion Criteria:

1. Centers for Disease Control and Prevention Category C at baseline or presenting with clinical symptoms suggestive of opportunistic infections precluding rapid ART initiation per EACS guidelines 2020.
2. Alanine aminotransferase (ALT) >5 times upper limit normal (ULN) - Subjects with severe hepatic impairment (Child-Pugh score>9).
3. eGFR<30 ml/min
4. Any serious medical condition which would compromise the safety of the subject. Subject has a pre-existing mental, physical, or severe substance abuse disorder that may interfere with the subject's ability to comply with the dosing schedule and protocol evaluations and assessments. Subject has a condition or disorder which may interfere with drug absorption or render the subject unable to take oral medication.
5. Subject is, in the opinion of the Investigator, unable to complete the study dosing period and protocol evaluations and assessments. Patients with alcohol and drug use problems that in the view of the Investigator will compromise participation in the study.
6. Subject has any acute laboratory abnormality at screening, which, in the opinion of the Investigator, would preclude the subject's participation in the study. Any verified grade 4 abnormality would exclude a subject from participation in the study.
7. Subject is receiving or has received within 14 days prior to screening, any drug that has been classified as contraindicated from use with BIC/FTC/TAF
8. Pregnant or breast-feeding subjects.
9. Participation in another clinical trial.

HIV-positive PWID subjects that enroll in the study within 7 days from the first visit in the clinic and are treatment-naïve or have discontinued antiretroviral treatment (ART) for more than 3 months from enrollment.

The decision is depending on the scope that the data will be asked - in case of an interested project, the request will be evaluated